Anesthesiology
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Comparative Study
A comparison of alfentanil pharmacokinetics in children and adults.
The pharmacokinetics of alfentanil have been studied in eight children aged between 4 and 8 yr and five adults during general anesthesia. All patients were given 20 micrograms/kg alfentanil as an intravenous bolus injection. Plasma concentrations were measured at intervals up to 6 h by radioimmunoassay. ⋯ The shorter elimination half-life could be due to the smaller total apparent volume of distribution in children. Plasma protein binding was comparable between children and adults and could not explain the smaller volume of distribution in children. It is suggested that the smaller volume of distribution of alfentanil in children is a result of the decreased percentage of fat tissue in children.
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The effect of isoflurane on median nerve somatosensory evoked potentials (MN-SSEPs) was studied in 15 patients. Anesthesia was induced with thiamylal and maintained with oxygen and isoflurane. MN-SSEPs were recorded in awake patients and after achieving 0.5, 1.0, 1.5, and 2.0% stable end-tidal concentrations of isoflurane. ⋯ N20 was not discernible in one out of 14 patients after 1.5% and in three out of ten patients after 2% isoflurane. These results indicate that subcortical potentials are less affected by isoflurane anesthesia than cortical potentials. Amplitude reduction of cortical potentials was more noticeable than either prolongation of peak latency or conduction time.(ABSTRACT TRUNCATED AT 250 WORDS)
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Isoflurane (ISF)-induced hypotension causes equal reductions of cerebral blood flow (CBF) and the cerebral metabolic rate for oxygen (CMRO2) so that no disturbance of cerebral energy stores or metabolites occurs. While hypocapnia during ISF-induced hypotension causes a further reduction of CBF, the effects on cerebral energy stores and metabolites produced by combining hypocapnia with ISF-induced hypotension are not known. This study examined the effect of hypocapnia (PaCO2 = 20 mmHg) on CMRO2, the electroencephalogram (EEG), and levels of adenine nucleotides, phosphocreatine, lactate, pyruvate, and glucose in brain tissue in 12 dogs during ISF-induced hypotension. ⋯ CMRO2 was reduced by approximately 27%. Thirty minutes after restoration of normocapnia with normotension, cerebral metabolites remained unchanged and CMRO2, and the power of the alpha, beta-1, and beta-2 spectra of the EEG returned to control values. These results suggest no adverse effect on cerebral metabolism or function during hypocapnia combined with ISF-induced hypotension.